COLONIE – Gov. Andrew Cuomo on Saturday backed a full Democratic takeover of the state Senate, as the liberal Working Families Party debated late into the night over whether to grant him its ballot line in November.

In video and phone addresses to the third party's convention, Cuomo for the first time called for a change in the Senate's leadership structure. He targeted the five-member Independent Democratic Conference, which partnered with Senate Republicans last year to share control of the chamber and keep the traditional Senate Democrats from power.

"We'll tell the IDC, the Independent Democratic (Conference), that either they announce they agree to come back to the (Democrats) or they will face primaries this year from our unified Democratic Party," said Cuomo, a Democrat.

The IDC, led by Sen. Jeff Klein, D-Bronx, first broke away from Senate Democrats in 2011, after Republicans won a slim majority at the polls. In late 2012, Democrats won back the majority, but Klein's group entered a power-sharing agreement with Republicans.

A spokesman for the IDC could not immediately be reached for comment late Saturday. A spokesman for Senate Republicans declined comment.

As of 10 p.m. Saturday, the party was continuing to debate whether to grant its endorsement to Cuomo or Zephyr Teachout, a Fordham University law professor and former aide to Howard Dean's 2004 presidential campaign.

Cuomo and his supporters, including New York City Mayor Bill de Blasio, had worked behind the scenes in recent days in an attempt to secure the liberal, union-backed party's ballot line in November. On Friday, party co-chair Karen Scharff had signaled the organization would likely grant its support to an independent candidate.

But Cuomo had the support of many of the 48,000-member party's leaders, including several unions representing private workers like the Communications Workers of America. By Saturday evening, the party's nominating committee appeared to be coalescing around Cuomo.

The split among party members, however, was apparent. When Cuomo was nominated, polite applause was drowned out in the hotel ballroom by a 20-second chorus of boos and hisses.

Zephry Teachout(Photo: Provided photo)

"The decision that we're making tonight is one of the most complex and challenging we've ever faced," said party co-chair Bob Master, a Cuomo supporter and political director of the Communications Workers of America's Northeast chapter. "I'm not going to make any bones about it."

As Master listed Cuomo's accomplishments — passage of same-sex marriage and gun-control laws among them — some members of the crowd heckled him. "He cut AIDS funding," one yelled. "Tax breaks for the rich!"

Cuomo already has picked up the Democratic nod, and will face off against Westchester County Executive Rob Astorino, a Republican who picked up the Conservative Party ballot line on Saturday.

Factions of the Working Families Party's state committee have been holed up in various conference rooms in a suburban Albany hotel for much of the day, attempting to whip enough votes for Cuomo or his challenger.

By backing a Democratic takeover of the Senate, Cuomo picked up support from some Working Families Party members who have long criticized the Senate's current structure. But he risks alienating the Senate's leadership with 12 days remaining in the 2014 legislative session.

Earlier this week, Cuomo said he would consider it a "failure" if the coalition doesn't pass a broad system of public financing of political campaigns — a major priority of the Working Families Party that is opposed by Republicans.

The stakes are high for the influential, labor-backed third party, which has traditionally backed Democrats. The party's gubernatorial candidate must get at least 50,000 votes to retain its position on New York ballots. In 2010, it received about 150,000 votes with Cuomo as its nominee.